Beam-compass.



No. 673,687. Patented May 7, IQOL' s. L. PENFIELD. BEAM COMPASSES.

(Application filed Dec. 31, 1900.)

(I0 Model.)

UNITED STATES PATENT OFFICE.

SAMUEL L. PENFIELD, OF NEW HAVEN, CONNECTICUT BEAM-COMPASS.

SPECIFICATION forming part of Letters Patent N 0. 673,687, dated May '7, 1901.

Application filed December 31, 1900. Serial No. 41,562. (No model.)

To all whom it may concern.-

Be it known that I, SAMUEL L. PENFIELD, of New Haven, in the county of New Haven and State of Connecticut, have invented a new Improvement in Beam-Compasses; and I do hereby declare the following, when taken in connection with the accompanying drawings and the figures of reference marked thereon, to be a full, clear, and exact description of the same, and which said drawings constitute part of this specification, and represent, in

Figure 1, aperspective view of my improved beam-compass; Fig. 2, a view thereof in vertical section through the movable head; Fig. 3, a detached perspective view of the arm of the movable head; Fig. 4:, a detached reverse perspective view of the plate-like pencilclamp; Fig. 5, a broken view, in vertical section, showing the mode of using the temporary centering-block; Fig. 6, a broken plan view showing the centering-block applied to a blackboard with its corners registered with two lines drawn thereupon at right angles to each other.

My invention relates to an improvement in beam-compasses, the object being to produce at a low cost for manufacture an instrument which may be used in a great variety of situations for striking circles or arcs of circles in doing practical Work or in theoretical demonstration.

\Vith these ends in view my invention consists in a beam-compass having certain details of construction and combinations of parts, as will be hereinafter described, and pointed out in the claims.

In carrying out my invention as herein shown I employ a long beam 2, of uniform rectangular cross-section and having its outer face provided with grad uation-marks3,which may be varied in number and character as desired, or the marks may be left off altogether. This beam is furnished at one end with a fixed arm at, tapering in general outline and formed in the upper end of its outer face with a transverse groove 5 to receive the inner end of the beam, which is socured in place in the said groove by means of two screws 6 or in some other effective way. The lower end of this arm has inserted into it a centering-point 7, by preference made of metal, though hard wood would answer the purpose. ing head comprising a plate-like arm 8, a plate-like beam-clamp 9, and a plate-like pencil-clamp 10. The said arm 8 is tapering in general outline and formed near the upper end of its outer face with a transverse groove 11, which receives the beam 2, over which the sectional head is movable back and forth. The said groove 11 is, however, made just shallow enough so that the front face of the beam will project sufficiently out of the groove, and therefore beyond the outer face of the arm 8, to be impinged upon by the inner face of the plate-like beam-clamp 9. This clamp 9 consists of a rectangular piece or block of wood, having its inner face slightly convexed and formed near its upper edge with an opening 12, larger in diameter than the shank of a screw 13, which is passed through it into the upper end of the arm 8, to which the said clamp is thus permanently secured with a capacity for being canted. The said clamp 9 is drawn down upon the beam 2 for gripping the same, and thus securing the sectional head thereto, by means of a thumb-nut 14, mounted upon the threaded outer end of a clamping-nut 15, passed forward through the upper portion of the arm 8 at a point slightly below the groove 11 and through an enlarged opening 16, formed in the beam-clamp 9 to receive it, near the lower edge thereof, as also shown in Fig. 2. By loosening the thumb-nut 14 the friction between the beam-clamp and the beam is sufficiently reduced to permit the head to be moved freely along the beam. After the sectional head has been placed in the desired position upon the beam it is very readily gripped thereto by turning the thumb-nut 14, so as to cause the beam-clamp 9 to again bite the beam, at which time, however, it does not make contact with the front face of the arm 8. In using the device the graduations3 upon the beam 2 are read from the right-hand edge of the beam-clamp 9, which is for that purpose cut away, as at 9*, to form the comparatively thin edge 9*. The arm 8 of the sliding head is also formed with a vertical groove 17, located near its forward or outer edge and designedto receive the pencil, chalk, or stylus 18, or whatever the marking instrument employed may be. For convenience I shall Upon the beam 2 I mount a slidaction thereupon.

use the word pencil as a generic term to cover any marking instrument. The said groove 17 coacts in receiving the pencil with a corresponding groove 17, formed in the forward edge of the inner face of the plate-like pencil-clamp 10, which is attached to the lower end of the arm 8 by means of a screw 19, passing through a hole 20, formed in the upper portion of the clamp, and into the arm 8, as shown in Fig. 2, the hole 20 being enough larger than the diameter of the screw 19 to permit the clamp 10 to have a slight canting The said clampis drawn down upon the pencil, so as to secure a firm bite for the same, by means of a thumb-nut 21, mounted upon the projecting outer end of a clamping screw 22, passed forwardly through the lowerend of the arm 8 and through an enlarged opening 23, formed in the lower end of the clamp, which is loosened to permit it to be canted sufficiently away from the inner face of the arm 8 to permit the pencil 18 to be shoved into the grooves 17 and 17 by reversing the said nut. A bite is secured upon the pencil by tightening the thumb-nut 21 by turning it in the opposite direction.

For convenience in using my improved beam-compass upon blackboards and also to avoid scratching or otherwise disfiguring the same I by preference provide the instrument with a small square block 25, having a centering-hole 26 formed in its outer face for the reception of the centering-point 7, before mentioned. The inner face of this block has secured to it a square piece 27, of rubber or equivalent material, and the block is attached by acord 28 to a screw 29,entered into the front face of the fixed arm at. In usingthisblock it may be very accurately placed upon a blackboard, for instance, by drawing two lines 30 31 at right angles to each other thereupon, as shown in Fig. 6, in which a small section of a blackboard is designated by 32. The block 25 is now placed upon the blackboard with its corners exactly registered with the lines 30 and 31, which necessarily brings the centering-point 26 of the block directly over the intersection of the lines,which are in tersected at the point which it is desired shall constitute the center upon which the beam-compass wil l theoretically turn. The centeringpoint 7 of the instrument is now placed in the centering-hole 26, as shown in Fig. 5, and the grip of the rubber 27 upon the board will be such that the block will not slip when the compass is being used. In this way scratching or disfiguring the blackboard is avoided without any loss of accuracy in the use of the instrument.

By preference the instrument will be made of wood, though that is not essential, and it is obvious that the dimensions and formsof the parts entering into it may be varied without departing from my invention. I would therefore have itunderstood that I do not limit myself to the exact construction herein shown and described, but hold myselfat liberty tov respect thereto.

2. In a beamcom pass,the combination with a beam, of a fixed arm secured to one end thereof, and a sliding head mounted upon the beam and comprising a plate-like arm, a plate-like beam-clamp attached to the upper end of the said plate-like arm, and a platelike pencil-clamp attached to the said platelike arm at a point below the lower end of the said plate-like beam-clamp.-

3. In a beam-compass,the combination with a beam, of a fixed arm secured to one end thereof, and a sliding head mounted upon the said beam and comprising a platelike arm formed with a transverse groove for the reception of the beam, a plate-like beam-clamp secured to the upper end of the said arm so as to impinge upon the outer face of the beam which projects out of the groove in the said arm, and a plate-like pencil-clamp secured to the said plate-like arm at a point below the lower end of the said plate-like beam-clamp.

4:. In abeam-compass,the combination with a beam, of a fixed arm secured to one end thereof, and a sliding head formed at its up. per end with a transverse groove for the reception of the beam, and with a vertical groove for the reception of a pencil, of a plate-like beam-clamp secured to the said plate-like arm at a point above the said transverse groove, and a plate-like pencil-clamp secured to the said plate-like arm at a point below the lower end-of the said plate-like beam-clamp, and means for securing the said plate-like clamps to the said plate-like arm.

5. In a bcam-compass,the combination with a beam, of a fixed arm secured to one end thereof and provided with a centering-point, a sliding head mounted upon the beam, and a button movably connected with the compass, and formed with a centering-hole for the direct reception of the centering-point which turns in the button and prevents the disfigurement of the blackboard.

In testimony whereof I have signed this specification in the presence of two subscribing witnesses.

SAMUEL .L. PENFIELD.

Witnesses:

FRED O. EARLE, GEORGE D. SEYMOUR. 

